1. Technical Field
The present invention relates to a length measuring arrangement
2. Background Information
Such length measuring arrangements, such as for example described in DE 28 10 341 C2, are employed for measuring lengths as well as distances, and are in particular used in processing machinery for measuring the relative movement of a tool in relation of a workpiece to be processed, in coordinate-measuring machinery, and increasingly also in the semiconductor industry.
Here, a scale with a measuring graduation, which is protected from environmental effects, is used as the measurement representation and is placed into a housing, which extends linearly in the measuring direction. For simple and cost-effective manufacture, the housing is an extruded profile made of a non-magnetic material, in particular aluminum. In the course of position measurement, the measuring graduation, which is incrementally or absolutely coded, is scanned by a scanning carriage. For this purpose, the scanning carriage is linearly conducted along two guide faces extending perpendicularly in relation to each other and is pressed against them. This guidance has proven itself, because it is assured that a constant scanning distance between the scanning carriage, in particular the scanning plate, and the scale is maintained over the entire measurement length, which guarantees the good quality of the scanning signal. The guidance of the scanning carriage is decoupled from the guidance of the object to be measured in that a mounting piece with a coupling is provided between the object to be measured and the scanning carriage, which coupling couples the scanning carriage rigidly to the mounting piece in the measuring direction and resiliently transversely to it. Pressing the scanning carriage against the two guide faces of the scale, which extend perpendicularly in relation to each other, i.e. the generation of the pressing force, takes place in the prior art by a spring arm (DE 23 49 944 A1), or by several pressure springs, wherein each of the guide feces is provided its own spring (DE 28 10 341 C2), whose pressure force is oriented toward the respective guide face. As a rule, these springs, which are oriented perpendicularly to each other, are arranged between the scanning carriage and the mounting piece, this leads to the distance between the scanning carriage and the mounting piece having an influence on the pressure forces. It is therefore necessary to select the installation tolerances to be particularly small.
The demands made on length measuring arrangements are continuously increasing, higher resolution, as well as greater accuracy and reproducibility of the position measurement is continuously being demanded. Along with this, a compact mechanical structure should be provided, and the length measuring arrangement should be produced in a cost-effective manner.